<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>

</head>

<body>
  <div id="app">
    <button @click="add">添加a数据</button>
    <div v-if="isShow">
      <button @click="change">修改a数据</button>
      {{a}}
    </div>
  </div>
  <script src="./vue.global.js"></script>
  <script>
    const { createApp } = Vue;
    const app = createApp({
      data() {
        return {
          isShow: false
        }
      },
      methods: {
        add() {
          this.a = '这是动态添加给实例的数据';
          this.isShow = true;
        },
        change(){
          this.a = '值改变了';
        }
      },
    })
    app.mount('#app')
  </script>
</body>

</html>